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namei.c: take "jump to root" into a new helper

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... and use it both in path_init() (for absolute pathnames) and
get_link() (for absolute symlinks).

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2015-12-05 20:51:58 -05:00
parent ef55d91700
commit 248fb5b955
1 changed files with 26 additions and 28 deletions
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54
fs/namei.c
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@ -841,6 +841,26 @@ static inline void path_to_nameidata(const struct path *path,
nd->path.dentry = path->dentry;
}
static int nd_jump_root(struct nameidata *nd)
{
if (nd->flags & LOOKUP_RCU) {
struct dentry *d;
nd->path = nd->root;
d = nd->path.dentry;
nd->inode = d->d_inode;
nd->seq = nd->root_seq;
if (unlikely(read_seqcount_retry(&d->d_seq, nd->seq)))
return -ECHILD;
} else {
path_put(&nd->path);
nd->path = nd->root;
path_get(&nd->path);
nd->inode = nd->path.dentry->d_inode;
}
nd->flags |= LOOKUP_JUMPED;
return 0;
}
/*
* Helper to directly jump to a known parsed path from ->follow_link,
* caller must have taken a reference to path beforehand.
@ -1017,21 +1037,8 @@ const char *get_link(struct nameidata *nd)
if (*res == '/') {
if (!nd->root.mnt)
set_root(nd);
if (nd->flags & LOOKUP_RCU) {
struct dentry *d;
nd->path = nd->root;
d = nd->path.dentry;
nd->inode = d->d_inode;
nd->seq = nd->root_seq;
if (unlikely(read_seqcount_retry(&d->d_seq, nd->seq)))
return ERR_PTR(-ECHILD);
} else {
path_put(&nd->path);
nd->path = nd->root;
path_get(&nd->root);
nd->inode = nd->path.dentry->d_inode;
}
nd->flags |= LOOKUP_JUMPED;
if (unlikely(nd_jump_root(nd)))
return ERR_PTR(-ECHILD);
while (unlikely(*++res == '/'))
;
}
@ -2015,26 +2022,17 @@ static const char *path_init(struct nameidata *nd, unsigned flags)
}
nd->root.mnt = NULL;
nd->path.mnt = NULL;
nd->path.dentry = NULL;
nd->m_seq = read_seqbegin(&mount_lock);
if (*s == '/') {
if (flags & LOOKUP_RCU)
rcu_read_lock();
set_root(nd);
if (flags & LOOKUP_RCU) {
nd->seq = nd->root_seq;
nd->path = nd->root;
} else {
path_get(&nd->root);
nd->path = nd->root;
}
nd->inode = nd->path.dentry->d_inode;
if (!(flags & LOOKUP_RCU))
if (likely(!nd_jump_root(nd)))
return s;
if (likely(!read_seqcount_retry(&nd->path.dentry->d_seq, nd->seq)))
return s;
if (!(nd->flags & LOOKUP_ROOT))
nd->root.mnt = NULL;
nd->root.mnt = NULL;
rcu_read_unlock();
return ERR_PTR(-ECHILD);
} else if (nd->dfd == AT_FDCWD) {